Deck 11: Liquids

Question 1

Explain why many nonpolar molecules, such as benzene and hexane, are liquids at room temperature.

Answer 1

Fritz London explained that the temporary fluctuations in the electron distributions within atoms and nonpolar molecules could result in the formation of short-lived instantaneous dipole moments. The instantaneous dipole moment on one atom can interact with the electrons in an adjacent atom, pulling them toward the positive end of the instantaneous dipole or repelling them from the negative end. The net effect is that the first atom causes the temporary formation of a dipole, called an induced dipole, in the second. Interactions between these temporary dipoles cause atoms to be attracted to one another. These attractive forces are called London dispersion forces. Hence nonpolar substances are liquids at room temperature.

Question 2

Which of the following statements is true regarding the properties of liquids?

A) Liquids are much denser than solids.
B) Liquids can be readily compressed.
C) The density of water varies significantly over a narrow temperature range.
D) Liquids can adopt the volume of their containers.
E) The mean free path in liquids is very short.

Answer 2

The mean free path in liquids is very short.

Question 3

The compounds, potassium cyanide, diethylether, and cyclobutane when arranged in an increasing order of their boiling points, will follow the order:

A) potassium cyanide ˂ diethyl ether ˂ cyclobutane.
B) potassium cyanide ˂ cyclobutane ˂ diethyl ether.
C) diethyl ether ˂ cyclobutane ˂ potassium cyanide.
D) cyclobutane ˂ potassium cyanide ˂ diethyl ether.
E) cyclobutane ˂ diethyl ether ˂ potassium cyanide.

Answer 3

cyclobutane ˂ diethyl ether ˂ potassium cyanide.

Question 4

Why do liquids adopt the shape, but not the volume of their containers?

Question 5

The arrangement of molecules in a _____ is completely random.

Question 6

The intermolecular interactions that result between molecules with net dipole moments are called _____.

A) instantaneous dipole moments
B) dipole-dipole interactions
C) dipole-ion interactions
D) London dispersion forces
E) hydrogen bonds

Question 7

HCl is a liquid at room temperature and 1 atm pressure.

Question 8

London dispersion forces get stronger with increasing molecular size for similar substances.

Question 9

The density of a liquid is commonly measured in units of _____.

Question 10

The rate of diffusion in liquids is faster than that in gases.

Question 11

Why is ice less dense than liquid water?

Question 12

A three fold increase in the distance between two dipoles of adjacent molecules:

A) decreases the strength of interactions by 64 fold.
B) increases the strength of interaction by 2⁶.
C) has no influence on the strength of interactions between the dipoles.
D) decreases the strength of interactions by 729 fold.
E) decreases the strength of interactions by 216 fold.

Question 13

Which of the following is true of the molecular order of liquids?

A) The arrangement of molecules in liquids is completely random.
B) The molecules have a lower kinetic energy compared to the molecules in a solid.
C) The molecules in a liquid can move freely within the system without colliding with each other.
D) The molecules exhibit short-range order because of strong intermolecular attractive forces.
E) The molecules in a liquid are arranged in a repeating three-dimensional array.

Question 14

Which of the following compounds has the highest boiling point?

A) Cyclobutane
B) Acetone
C) Dimethyl sulfoxide
D) Diethylether
E) Hydrogen cyanide

Question 15

The ease of deformation of the electron distribution in an atom or molecule is called its _____.

Question 16

The kinetic energy of water molecules depends on their temperature.

Question 17

Intramolecular forces hold molecules together in a liquid.

Question 18

A short-lived dipole moment that is created in atoms and nonpolar molecules adjacent to atoms or molecules with an instantaneous dipole moment is called a(n) _____.

Question 19

The arrangement of molecules in a liquid is in a repeating three-dimensional array.

Question 20

A(n) _____ is a strong dipole-dipole interaction that results when hydrogen is bonded to electronegative elements such as oxygen, nitrogen and fluorine.

Question 21

The upper surface of a liquid in a tube is called the _____.

Question 22

How do the relative strengths of cohesive and adhesive forces determine the level to which a liquid rises in a capillary tube?

Question 23

Viscosity of a liquid is defined as:

A) the ratio of the liquid's volume to its mass.
B) the energy required to increase the outer area of a liquid by a specific amount.
C) the mass of a liquid per unit volume.
D) the resistance of a liquid to flow.
E) the tendency of the liquid to rise against gravity.

Question 24

Which of the following is a volatile liquid?

A) Glycerine
B) Acetone
C) Ethylene glycol
D) Water at 60^oC
E) Mercury

Question 25

The surface tension of a liquid is measured in units of _____.

A) g/cm3
B) J/˚C
C) Pa·s
D) J/m²
E) J/cm²

Question 26

Explain with an example, the practical importance of controlling the viscosity of liquids.

Question 27

Which of the following has the lowest vapor pressure?

A) Ethylene glycol
B) Acetone
C) Water at 60^oC
D) Diethyl ether
E) Gasoline

Question 28

The intermolecular forces that hold a liquid together are called _____.

Question 29

Condensation is a physical process by which the atoms or molecules:

A) in the liquid phase enter the gas phase.
B) in the vapor phase enter the solid phase.
C) in the vapor phase enter the liquid phase.
D) in the solid phase enter the liquid phase.
E) in the solid phase enter the gas phase.

Question 30

The rate of condensation depends only on the surface area of the liquid and is essentially constant.

Question 31

Which of the following statements is true of the capillary action of liquids?

A) The capillary action of a liquid entirely depends on the strength of the adhesive forces.
B) If the adhesive forces are weaker than the cohesive forces, then the liquid in the capillary rises to the level where the downward force of gravity exactly balances this upward force.
C) If the cohesive forces are stronger than the adhesive forces, the liquid in the tube will have a convex meniscus.
D) If the cohesive forces are weaker than the adhesive forces, the liquid pulls itself down into the capillary below the surface of the bulk liquid to minimize contact with the glass.
E) If the cohesive forces are weaker than the adhesive forces, the liquid in the tube will have a convex meniscus.

Question 32

A sphere has the smallest possible surface area for a given volume.

Question 33

The molecules that are present only at the surface of a liquid can undergo evaporation.

Question 34

Which of the following polar liquids will exhibit a high capillary action?

A) mercury
B) acetone
C) olive oil
D) glycerol
E) liquid methane

Question 35

The equilibrium vapor pressure of a liquid strongly depends on the amount of liquid present.

Question 36

The physical process by which atoms or molecules in the liquid phase enter the gas phase is known as _____.

A) sublimation
B) condensation
C) deposition
D) fusion
E) vaporization

Question 37

Which of the following has the highest viscosity?

A) Ethanol
B) Chloroform
C) Castor oil
D) Milk
E) Gasoline

Question 38

_____ is a unique property of water that helps in the transportation of fluids and nutrients, from the roots to the top of trees through the trunks.

Question 39

Viscosity decreases with the increasing molecular size.

Question 40

Water has a convex meniscus.

Question 41

A change of state that occurs when any of the three forms of matter is converted to either of the other two is called a(n) _____.

Question 42

The pressure exerted by a vapor in dynamic equilibrium with its liquid is the _____ of the liquid.

Question 43

The enthalpy change that accompanies the conversion of a solid directly to a gas is called enthalpy of _____.

A) combustion
B) sublimation
C) fusion
D) vaporization
E) solution

Question 44

In the Clausius-Clapeyron equation, ln P = $\left( \frac { - \Delta H _ { v a p } } { R } \right) \left( \frac { 1 } { T } \right) + C { }{ , R}$ represents:

A) heat of vaporization
B) vaporization
C) absolute temperature
D) universal gas constant
E) Clapeyron constant

Question 45

The enthalpy of vaporization of a given substance is greater than its enthalpy of fusion.

Question 46

Which of the following physical processes is a reverse of the process of sublimation?

A) Condensation
B) Deposition
C) Fusion
D) Freezing
E) Vaporization

Question 47

The vapor pressure of methanol at 50.0˚C and 65.0˚C is 400.0 and 760.0 torr respectively. The enthalpy of vaporization of methanol will be _____ kJ/mol.

A) 3.89
B) 391
C) 38.8
D) 107
E) 65.0

Question 48

A supercritical fluid has a density which is almost the same as the density of the gas phase.

Question 49

Phase changes are always accompanied by a change in the temperature of the system.

Question 50

A(n) _____ refers to an unstable liquid at a temperature and pressure at which it should be a gas.

A) ionic liquid
B) superheated liquid
C) supercooled liquid
D) supercritical fluid
E) viscous liquid

Question 51

The physical process of conversion of a solid to a liquid is known as _____.

A) sublimation
B) condensation
C) evaporation
D) fusion
E) deposition

Question 52

The _____ refers to the pressure created over a liquid by the molecules of a liquid substance that have enough kinetic energy to escape to the vapor phase.

Question 53

A metastable liquid phase that exists below the normal melting point of a substance is known as _____.

A) Ionic liquid
B) Superheated liquid
C) Supercooled liquid
D) Supercritical fluid
E) Superheated steam

Question 54

A(n) _____ is a solid sample of a substance that can be added to a supercooled liquid or a supersaturated solution to help induce crystallization.

Question 55

Explain why there is no change in temperature during a phase change.

Question 56

What is dynamic equilibrium? Why there is no equilibrium established in the case of a liquid in an open container?

Question 57

Which of the following is an endothermic process?

A) Conversion of supercooled liquid to glass.
B) Liquefaction of natural gas.
C) Formation of frost on leaves.
D) Loss of snow due to sunshine activity.
E) Corrosion of metals.

Question 58

The vapor pressure of liquid water at 58.0˚C and 73.0˚C is 136.1 and 265.7 torr respectively. The vapor pressure of liquid water at 69.0˚C is _____ torr.

A) 137
B) 425
C) 223
D) 265
E) 416

Question 59

The transition from a solid to a gas is exothermic, as it releases energy.

Question 60

Which of the following processes best exemplifies the process of sublimation?

A) Coal liquefaction
B) Melting of snow
C) The process of crystallization
D) The process of distillation
E) Iodine producing fumes on heating

Question 61

Molten salts are good conductors of electricity.

Question 62

_____ are substances that are liquids at room temperature and pressure due to their disorganized structure that results in a relatively low melting point.

A) Superheated liquids
B) Supercritical fluids
C) Ionic liquids
D) Molten salts
E) Supercooled liquids

Question 63

Which of the following lines in the given phase diagram, corresponds to a line along which the solid and liquid phases are in equilibrium?

A) The line that connects points B and D.
B) The line that connects points C and B.
C) The line that connects points A and B.
D) The line that connects points A and C.
E) The line that connects points A and D.

Question 64

Which of the following lines in the given phase diagram, represents the vapor pressure curve of the solid phase?

A) The line that connects points B and D.
B) The line that connects points C and B.
C) The line that connects points A and B.
D) The line that connects points A and C.
E) The line that connects points A and D.

Question 65

The line that connects points A and B in the given phase diagram is:

A) is the vapor pressure curve of the solid phase.
B) shows the melting point variation of a solid with pressure.
C) is the vapor pressure curve of the liquid phase.
D) is the vapor pressure curve of the gas phase.
E) shows the boiling point variation of a liquid with pressure.

Question 66

In a phase diagram, the region that corresponds to a combination of high pressure and low temperature favors _____ phase.

A) gas
B) supercritical fluid
C) supercooled liquid
D) solid
E) liquid

Question 67

When solid carbon dioxide is heated, it undergoes sublimation to form a gas.

Question 68

A gas phase is favored at high pressure and low temperature.

Question 69

The combination of temperature and pressure at which all three forms of matter can exist simultaneously is called the critical point.

Question 70

The combination of the critical temperature and critical pressure of a substance is called its _____.

Question 71

The point in a phase diagram that represents the only combination of temperature and pressure at which all three forms of matter are in equilibrium is called the _____ point.

A) equilibrium
B) critical
C) significant
D) triple
E) dominant

Question 72

A salt when heated to its melting point produces a(n) _____.

Question 73

What are ionic liquids? List any two applications of ionic liquids.

Question 74

Which of the following substances has the highest critical temperature?

A) Ammonia
B) Mercury
C) Carbon dioxide
D) Water
E) Ethanol

Question 75

The "_____" point of a substance is a combination of the highest temperature at which it can exist as a liquid and the minimum pressure needed to liquefy it at that temperature.

A) significant
B) dominant
C) superficial
D) critical
E) specific

Question 76

The single, dense fluid phase that exists above the critical temperature of a substance is called a(n) _____ fluid.

A) ionic
B) superheated
C) molten
D) supercritical
E) supercooled

Question 77

List out the general features of a phase diagram.

Question 78

A(n) _____ is a graphic summary of the physical state of a substance as a function of temperature and pressure in a closed system.

Question 79

Ionic liquids have low melting points.

Question 80

The region that corresponds to a combination of high temperature and low pressure in a phase diagram favours _____ phase.

A) supercritical fluid
B) gas
C) supercooled liquid
D) solid
E) liquid